HTML offers a number of tags that change the appearance of text. In
general, these tags can be grouped into two flavors: content-based
styles and physical styles.

In addition, the W3C has put forth a draft for a new standard way in
which HTML authors may control the look and layout of their document
text through Cascading Style Sheets. Netscape, too, in their latest
browser has implemented style sheets through JavaScript. We describe
the HTML tag-based text styles in this chapter. See
Chapter 9, Cascading Style Sheets, for details about
cascading and JavaScript-based style sheets.

Content-based style tags inform the browser that the enclosed text has
a specific meaning, context, or usage. The browser then formats the
text in a manner consistent with that meaning, context, or usage.

Because font style is specified via semantic clues, the browser can
choose a display style that is appropriate for the user. Since such
styles vary by locale, using content-based styles helps ensure that
your documents will have meaning to a broader range of readers. This
is particularly important when a browser is targeted at blind or
handicapped readers whose display options are radically different from
conventional text or are extremely limited in some way.

The HTML standard does not define a format for each of the
content-based styles except that they must be rendered in a manner
different from the regular text in a document. The standard doesn't
even insist that the content-based styles be rendered differently from
one another. In practice, you'll find that many of these tags have
fairly obvious relationships with conventional print, having similar
meanings and rendered styles, and are rendered in the same style and
fonts by most browsers.

We use the word "intent" a lot when we talk about content-based style
tags. That's because the meaning conveyed by the tag is more important
than the way a browser displays the text. In some cases, however, you
might want the text to appear explicitly in italic or bold, perhaps
for legal or copyright reasons. In those cases, use a physical style
for the text.

While the tendency with other text-processing systems is to control
style and appearance explicitly, with HTML you should avoid explicit,
physical tags except on rare occasions. Rather, provide the browser
with as much contextual information as possible. Use the content-based
styles. Even though current browsers may do nothing more than display
their text in italic or bold, future browsers and various
document-generation tools may use the content-based styles in any
number of creative ways.